This invention relates to a fire-proof window comprising a single or double pane the edges of which, surrounded by a suitable sealing joint, are housed in grooves provided by a casing.
In known fire-proof windows, the glass is mounted directly in a groove of the casing, said groove being open on one side for this purpose. Then this pane is sealed by means of the sealing joint in the groove which has previously been closed off, for example by means of a window batten mounted on the casing.
When a window of this kind is fitted on the building site, first the casing is placed in the corresponding opening in the masonry and fixed thereto. Then the glass is positioned in the opening in the casing and sealed in the grooves provided in the latter.
During manufacture, it sometimes happens that the casing is not strictly right-angled, particularly in its large dimensions. It may be that the manufacturing tolerances of the casing are exceeded. Moreover, it may happen that the casing moves out of true when mounted in the masonry. In both cases, the opening defined by the bases of the grooves of the casing is out of true and takes on the approximate shape of a parallelogram or a trapezium instead of its normal rectangular form. In such cases, after the glass has been placed in the opening in question, the edges of the glass are not at a regular spacing from the base of the grooves, and the sealing joint is thicker at certain points on the perimeter of the glass. These points are weak points from the point of view of fire-proofing, since they permit the rapid passage of flames and hot gases in the case of fire.